1. Field of the Invention
The present invention relates to a multi-mode radio transmission system under environment available by means of a different radio communication mode.
2. Description of the Prior Art
In the present radio communication systems such as land mobile communication systems broadcasting systems, and satellite communication systems, a common transmission mode has not been determined, and a communication system is utilized on the basis of various standards.
For example, nowadays, in Japan, as digital mobile communication systems, PDC(Personal Digital Cellular) system and PHS(Personal Handy Phone) system are available. Moreover, even in Europe, GSM(Global System for Mobile Communications) system and the like has been operated.
These systems looks different each other, however these systems are based of Quadrature modulation.
As shown in FIG. 7, the Quadrature modulation is a method which can improve the transmission capacity more than two times with the use of two orthogonal axes alternatively at the same frequency. In the concrete, we use a characteristics of orthogonality between sine and cosine wave, in which the integration value during one cycle becomes to be zero when we multiply sine wave by cosine wave and integrate the multiplied value.
In the configuration for a transmitter as shown in FIG. 7, input transmission data signal is divided into two chapels of Ich(In phase channel) and Qch (Quadrature Phase Channel). Then the data of Ich is multiplied by a signal generated from one sign wave source, and the data of Qch is multiplied by a signal which is phase-shifted in 90 degrees for aforesaid sine signal. Finally, these two signals of Ich and Qch are synthesized together.
On the other hand, in a receiver, a signal is recovered by means of performing a reversible operation for the transmitter.
As described above, in an environment, in which a plurality of radio communication systems exist, a user must possess a radio terminal for a radio communication service. In other wards, in the case of utilizing a plurality of communication services, a user must have many radio terminals to all the radio communication systems.
In order to reduce the number of terminal, it is prefer to be able to integrate a plurality of radio transmission mode into a radio terminal.
For one of the solutions for the integration of several radio communication systems, xe2x80x9cSoftware Radioxe2x80x9d concept has been proposed. In the software radio concept, we describe all functions for modulation and demodulation in each radio communication terminal as programs for Digital Signal Processing Hardware(DSPH) like FPGA and DSP. By changing the programs in accordance with users"" request, we operate all radio communication system with a radio terminal.
However, in conventional concept of software radio, we often change all the configuration programs for a radio communication system whenever a radio transmission system must be changed.
Moreover, the configuration program is written in a high level computer language like xe2x80x9cCxe2x80x9d language or a low level computer language as assembler. Accordingly, we must prepare several nonvolatile memories for storing a plurality of programs. From the viewpoint of costs, we needs more time for delivering the software radio as the consumer products.
Further, the other method exists, in which all functions configured several radio communication systems has already implemented in the radio communication terminal in advance.
However, in this case, we must equip all the components in a radio terminal whether users use all communication systems or not. Therefore from the viewpoint of cost and miniaturizing, the method is not the best solution for the integration of radio terminal. Moreover, in advance, we write all functions of transmitter and receiver for a radio communication system into a ROM(Read Only Memory) card. Then, by exchange such ROM cards, we realize multimode terminal.
But, in the case of usage of ROM card, users always must have several ROM cards. From the viewpoint of portability, we need refinement of the idea.
The present invention carried out in order to solve the above-mentioned problem. In the invention, there is a technical characteristic in a point of aiming a difference of system configuration between the recent radio communications.
Concretely, in PHS system and the other systems, the Quadrature modulator is common by providing the selective differential information, which comprises valuable coefficient information writing a differential part between each kind of radio modulation and demodulation scheme, and their address on the DSPH into aforesaid reconfiguable modulation and demodulation function part, we realize our required radio communication terminal. Moreover a selective differential information can be supplied from a base station in an area, in which a radio terminal is used by download.
In the invention, under the circumstance in which several radio communication systems can be utilized, in order to realize several modulation and demodulation schemes of such systems by a communication terminal, the necessary common modulation and demodulation function part such as an orthogonal phase modulator, an automatic gain control part and quasi-synchronized orthogonal detector, and the reconfigurable modulation and demodulation function part which can realize all components related to modulation and demodulation schemes except for the components of common function part by changing parameters, are installed at a mobile base station. With functional selective means which can be activated by providing the selective differential information, which comprises variable coefficient information writing a different part between each kind of radio modulation and demodulation scheme and their address on the DSPH from control station into aforesaid reconfigurable modulation and demodulation function part of a radio base station, the base station can realize several radio communication system.
As described above, by using the multimode terminal of present invention, it is easy to make the size of terminal small and light and reduce a producing cost, in comparison with installing a communication functional means for all of radio communication modes possible to utilize.
Moreover, as for the selective information supplying to a functional selecting means in order to switch a communication mode, it is a simple information only to select a function being effective within a different functional part, transferring from a base station via a radio becomes also to be possible and storing beforehand to a terminal side is easy. Further, as a radio transmission system according to one feature of the present invention, if a common functional part, a differential part and a functional selecting means are installed at a radio base station, the change of a communication mode at a radio station becomes to be possible.